JPS62137742A - Information recording disk - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information recording disc that records and reproduces information by irradiating it with a light beam, and more specifically relates to an information recording disc that is equipped with a plastic transparent substrate. The present invention relates to coating of the substrate in an information recording disc.

[Conventional technology]

Conventionally, at least one of an information signal and a tracking signal is recorded in the form of an uneven pattern on one side of a transparent substrate, and information is recorded and reproduced by irradiating a light beam along the uneven pattern. A disc for recording information is known.
Publication No. 9).

FIG. 3 is a sectional view of a conventionally known information recording disk of this kind, in which 1 is a transparent substrate, 2 is a resin layer on which a concavo-convex pattern 3 such as pre-pits and pre-groups has been transferred;
Reference numeral 4 indicates a recording film made of a recording material formed on the surface of this resin layer 2.

This figure shows a double-sided information recording disc in which two transparent substrates 1.1 are bonded with the recording film 4 facing inward. A single-sided recording type information recording disk in which a transparent substrate and a protector having substantially the same shape are bonded is also known.

By the way, the above-mentioned transparent substrate 1 has 1) high light transmittance, 2) excellent weather resistance and chemical resistance, 2) high surface hardness, and 2) low optical anisotropy (retardation). Attributes such as that are required. Traditionally, glass substrates have been used to satisfy all of these attributes, but glass substrates have the problem of being difficult to mold, resulting in high manufacturing costs, and in recent years, PMM
Plastic transparent substrates such as A and polycarbonate have become widely used.

[Problems with conventional technology]

However, since plastic transparent substrates have lower surface hardness than glass substrates, there is a problem in that scratches and other scratches are easily formed on the surface of the substrate during manufacture or use.

As mentioned above, this type of information recording disk has a transparent substrate 1.
Information is written on the recording film 4 by irradiating the recording film 4 with a light beam from the outside, and the information is read out by detecting the reflected light from the recording film 4. When the surface of the substrate 1 is damaged, the light beam and its reflected light may be reflected, refracted, or
This causes serious problems such as diffraction and the like, making it difficult to record and reproduce normal signals.

[Means for solving problems]

The present invention solves the above-mentioned problems that may occur when using a plastic transparent substrate, and provides an inexpensive and highly reliable information recording disc by forming an uneven pattern on a plastic transparent substrate. It is characterized by having a thin film made of a transparent inorganic material coated on the side opposite to the side surface.

〔Example〕

FIG. 1 shows a sectional view of an information recording disk according to the present invention. In this figure, reference numeral 5 indicates a thin film coated on the surface of the transparent substrate, and other members similar to those shown in FIG. 3 are designated by the same reference numerals.

The material constituting the thin film 5 may be any material that is harder and more transparent than the plastic material constituting the transparent substrate 1. However, from the viewpoint of not degrading the playback signal level compared to conventional information recording discs, the thin film 5 has a light transmittance of 97% or more, and the coating of the thin film 5 has a higher light reflectance than conventional discs. It is preferable that the value does not become large.

As the transparent substrate 1, PMMA (polymethyl methacrylate), PC (polycarbonate), epoxy resin, etc. are used. The hardness of PMMA and epoxy resin is 2H on the pencil hardness scale, and the hardness of PC is also 2H on the pencil hardness scale.
It is B. Note that these hardness measurements were performed using a Tallemens type scratch hardness meter.

In addition, the refractive index of PMMA (wavelength of inspection light 830 mn+)
is about 1.49. The refractive index of PC is about 1.58, and the refractive index of epoxy resin is about 1.51.

As for the substance constituting the thin film 5, an inorganic material is more advantageous than a batter material in terms of hardness, and is selected from metals, nonmetals, and semiconductor fluorides, oxides, nitrides, and carbides. Among these, CeFff, MgFz.

NdFs, 5iOz, SiO, TiO□, Alz
03, SiC, and 5iJn have a pencil hardness of 68 or more and are particularly preferred.

Furthermore, the thin film 5 can be formed on the surface of the transparent substrate 1 using any thin film forming substance to any desired thickness.

However, from the viewpoint of not degrading the reproduced signal level compared to conventional information recording disks, it is necessary to use materials and thicknesses that satisfy the phase and amplitude conditions for preventing reflection of incident light on the plastic transparent substrate 1. It is necessary to form the thin film 5 at this point.

That is, as shown in FIG. 2, if there is a transparent thin film 5 with a refractive index nI and a thickness dl on a substrate 1 with a refractive index nb, and there is air in addition to the thin film 5, the wavelength of light In order to prevent reflection, n, ad, = □λ... (1) n,
It is necessary to satisfy the following two conditions: = F (2). The above (1) 2 is called a phase condition for preventing reflection, and the equation (2) is called an amplitude condition.

If n, <nb, the reflection decreases; if rl, >n, the reflection increases.

Therefore, when the thin film 5 is formed using a material such as MgFz (rz = 1.38), which has a smaller refractive index than the plastic transparent substrate 1, the conventional information recording disk on which the thin film 5 is not formed The reflectance decreases compared to , and when the above two equations are satisfied, the reflectance becomes zero. In addition, a transparent substrate 1 made of PMMA or epoxy resin (
n b #1.49-1.51) to 5 iOz (n +
= 1.46), and when forming a thin film 5 of CeF3 (nb = 1.58),
n+=1.59~1.63) or NdFs (n+
= 1.60), when forming the thin film 5 using a material having a refractive index substantially equal to that of the transparent substrate 1, the thickness d of the thin film 5 is Instead, the reflectance of the information recording disk is equal to the reflectance of the transparent substrate 1. Furthermore, when the thin film 5 is formed using a substance having a refractive index larger than that of the transparent substrate 1, the reflectance generally increases, but nl·d,=~2
If the thickness of the thin film 5 is adjusted so that the reflectance is minimized, the reflectance can be made equal to that of a conventional information recording disk on which the thin film 5 is not formed.

Further, any known thin film forming means can be used to form the thin film III 5, but in order to form a film of a hard inorganic material to a uniform thickness, for example, vacuum evaporation, sputtering, ion It is preferable to use a vacuum film forming method such as brating.

Hereinafter, specific examples of the information recording disc according to the present invention will be shown.

First Example First, a PC transparent substrate having a desired concavo-convex pattern transferred onto one side was prepared by an injection method. Next, T was applied to the surface of the PC transparent substrate on which the concavo-convex pattern was formed.
An eSe-based recording film was formed to a thickness of 300 mm. Then,
A thin film of MgF2 was formed to a thickness of about 1,500 mm on the surface of the above-mentioned PC transparent substrate opposite to the surface on which the uneven backbone was formed using a planar magnetron type sputtering device.

The sputtering conditions were Ar pressure of 4 x 10-” Torr.
, RF power was 100W. Next, a protective plate made of a plastic disk similar to the PC transparent substrate is bonded to the surface of the information recording disk manufactured as described above on the side where the concavo-convex pattern is formed. A sandwich-type, single-sided recording type information recording disk was manufactured.

When the C/N ratio of the reproduced signal was measured for the information recording disk according to the above embodiment, it was found that the C/N ratio was improved by about 0.5 dB compared to the conventional information recording disk.

Second Example First, a transparent substrate made of PMMA was produced by an injection method. Subsequently, on one side of the PMMA transparent substrate,
A thin film made of MgF2 was formed to a thickness of 1500 mm by a vacuum deposition method. Next, the above PMMA is extracted from the master disc.
A concavo-convex pattern corresponding to an information signal, a tracking signal, etc. was transferred to the surface of the manufactured substrate opposite to the surface on which the MgFz thin film was formed by the 2P method. Next, a TeSe-based recording film was formed to a thickness of about 300 mm on the surface of the resin layer on which the uneven pattern was formed. Finally, an air sandwich type single-sided recording information recording disk similar to that of the first embodiment was manufactured by bonding the information recording disk thus manufactured and the protective plate.

The information recording disc of the second embodiment also has a C/N ratio of about 0.5 dB compared to the conventional information recording disc.
It turns out that it has been improved.

Third Example First, a transparent epoxy substrate with a desired uneven pattern transferred to one side was prepared by a casting method, and a TeSe-based recording film was applied to the surface of the epoxy transparent substrate on the side where the uneven pattern was formed by 300 people. formed to a thickness. Next, a thin film of SfO was formed to a thickness of approximately 1000 nm on the surface of the epoxy transparent substrate opposite to the surface on which the concavo-convex pattern was formed using a Brenner magnetron sputtering apparatus. The sputtering conditions are Ar pressure 2X 10-” Torr, RF power 1
It was 00W. Finally, by joining the information recording disc and the protective plate produced in this way,
An air sandwich type single-sided recording disk similar to the first example and the second example was manufactured.

〔Effect of the invention〕

As explained above, according to the present invention, the surface hardness of an information recording disk equipped with a plastic transparent substrate is increased, and the incidence of defects that occur during manufacturing or use can be reduced accordingly. can. Therefore, it is possible to improve the manufacturing yield and reduce costs, and to provide an information recording disk with excellent durability and high credibility.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an information recording disk according to the present invention, FIG. 2 is an explanatory view explaining the reflectance of a transparent substrate on which a thin film is formed, and FIG. 3 is a conventionally known one. FIG. 2 is a sectional view showing an example of an information recording disc. 1...Transparent substrate, 2...Resin layer, 3.
...Concave and convex pattern, 4...Recording film, 5.
...Thin film. Fig. 1 1° Transparent substrate 2, 4 Elbow fat striping 3° Irregularities / 4; Full collapse 5, thin film Fig. 2 Fig. 3

Claims (5)

[Claims] (1) At least one of an information signal and a tracking signal is recorded in the form of an uneven pattern on one side of a transparent plastic substrate, and information is recorded by irradiating a light beam along the uneven pattern. , in an information recording disk adapted to perform playback, a thin film made of a transparent inorganic material having a harder hardness than the plastic transparent substrate is provided on the surface of the plastic transparent substrate opposite to the surface on which the concavo-convex pattern is formed. An information recording disc characterized by being coated with. (2) In the information recording disk according to claim 1, fluorides, oxides of metals, nonmetals, and semiconductors,
This information recording disk is patented in that it is coated with a thin film made of an inorganic material made of nitride or carbide, which is harder and more transparent than a transparent plastic substrate. (3) In the information recording disk according to claims 1 and 2, the disc is made of an inorganic material so as to satisfy the phase and amplitude conditions for preventing reflection of incident light on the plastic transparent substrate. An information recording disc characterized by being coated with a thin film. (4) An information recording disk according to claims 1 to 3, characterized in that a vacuum film forming method is used as a coating means for the thin film made of an inorganic material. (5) In the information recording disk according to claims 1 to 4, CeF_3, MgF_2, NdF
_3, SiO_2, SiO, TiO_2, Al_2O_
3. An information recording disk characterized in that one side of a plastic transparent substrate is coated with a thin film made of an inorganic material selected from SiC and Si_3N_4.